In recent years olefin polymers have found extensive use in the preparation of a wide variety of products many of which come into contact with food products. It is well known that exposure to sunlight or other sources of ultraviolet light cause the degradation of olefin polymers. Such degradation is shown by a loss in the molecular weight of the polymer, by the development of color, and by a decrease in such physical properties as tensile strength to the point of mechanical failure. This type of degradation has in the past been dealt with by the incorporation in the polymer composition of certain additives which are effective to inhibit it.
U.S. Pat. No. 3,988,293 (Mills) deals with a stabilizer system for polyolefins. Polypropylene compositions are shown which contain stabilizing proportions of 2-hydroxy-4-n-octoxybenzophenone and distearyl pentaerythritol diphosphite. Such compositions are shown to be resistant to breakage upon flexing, after prolonged exposure in a Weather-Ometer at 180.degree..
U.K. Pat. No. 1,526,603 shows a process for preparing certain mixed aryl aliphatic phosphites, i.e., phosphites wherein the phosphorus atom(s) is linked through oxygen both to aromatic and aliphatic groups. The use of these phosphites as thermal stabilizers likewise is shown. Polypropylene compositions containing bis-(2,4-ditertiarybutyl) pentaerythritol diphosphite and the corresponding 2,6-ditertiarybutylphenyl isomer are shown to be relatively stable after four extrusions at 475.degree. C., a fifth extrusion at 525.degree. C. and heating of a 25-mil. thick sample at 150.degree. C. until failure.